MD5 is a primative. Many algorithms specify a hash/compression function (which MD5 is) or a permutation (which AES is) in how they work. Message authentication

MD5 is a primative. Many algorithms specify a hash/compression function (which MD5 is) or a permutation (which AES is) in how they work. Message authentication (HMAC) can use any compression function, key derivation can use any compression function, and so on. Even stream ciphers can use MD5. People implementing things that use crypto should only be using functions that are "Authenticated Encryption" which specify the full suite like AES-GCM (permutation function: AES, in Galios/Counter Mode), or "Key Derivation Function" (PBKDF2-HMAC-SHA2 or Argon2d-Blake2b). What they've done at AM is implement their own key derivation function using the MD5 primative and concatenation.